The effect of modified lysozyme treatment on the microflora, physicochemical and sensory characteristics of pork packaged in preservative gas atmospheres

Abstract

The aim of the study was to investigate the effect of modified lysozyme on the microflora, physicochemical and sensory characteristics of pork loin packaged in modified atmospheres and stored at 4 ± 1◦ C. Different gas compositions (M1 65:25:10 O2:CO2:N2; M2 50:40:10 O2:CO2:N2; M3 80:20 O2:CO2 ) were used. The microbiological parameters (APC, Enterobacteriaceae, Pseudomonas spp., lactic acid bacteria), physicochemical indexes (pH, colour) as well as a sensory attribute, i.e., aroma were analysed. Meat samples were tested after five, 12, 19, 23, and 28 days of storage. Changes in the qualities of pork were determined throughout the storage. The proportions of polymeric forms, hydrolytic activity and hydrophobicity were determined in the lysozyme preparation. Modified lysozyme exhibited higher hydrophobicity and lower hydrolytic activity than lysozyme monomer. The colour parameters L* and a* were not considerably affected by the addition of modified lysozyme. The sample with the modified lysozyme was given the highest score for aroma. In comparison with the monomer, the modified lysozyme exhibited greater antibacterial effect, especially against Pseudomonas and Enterobacteriaceae. Microbial growth rates in the sample with modified lysozyme, packaged in an atmosphere with the highest content of CO2 (total plate count 4.59 log CFU/cm2; moulds and yeasts 2.17 log CFU/cm2 ) were lower than those observed in the sample without lysozyme packed under M1 and M3 (20–25% CO2 ). The use of an atmosphere with gas composition and modified lysozyme considerably extended the shelf life of pork. The combination of the atmosphere with the highest content of carbon dioxide (50% O2, 40% CO2, 10% N2 ) and modified lysozyme resulted in the best effect. This strategy extended the shelf-life by more than 20%, as compared with the control sample without lysozyme, packaged in an atmosphere of 50:40:10 O2:CO2:N2 .